1. Field of the Invention
The present invention relates to a mobile unit managing network and a path establishing method to be used for the mobile unit managing network and more particularly to a method for setting up a hierarchy-type network.
The present application claims priority of Japanese Patent Application No. 2003-165839 filed on Jun. 11, 2003, which is hereby incorporated by reference.
2. Description of the Related Art
In a conventional mobile unit managing network based on host routing, as shown in FIG. 4, a hierarchy-type network is set up using one unit of a highest-layer router R1 as a root router in which each of routers Ra to Rf manages a path for each of mobile terminals MN1 to MN4, as disclosed in, for example, Japanese Patent Application Laid-open No. 2002-223219 (Pages 5 and 6, FIG. 1).
That is, the disclosed conventional mobile unit managing network includes the highest-layer router R1, intermediate-layer routers Ra and Rb, lowest-layer routers Rc to Rf, radio base stations BS1 to BS8, and mobile terminals MN1 to MN4 in which the highest-layer router R1 is connected to the routers Ra to Rf through wire and the radio base stations BS1 to BS8 are connected to mobile terminals MN1 to MN4 by wireless.
Path updating notification fed from each of the mobile terminals MN1 to MN4 is transmitted through each of the radio base stations BS1 to BS8 to each of the lowest-layer routers Rc to Rf from where the path updating notification is further transmitted to the highest-layer router R1. The highest-layer router R1 manages only a network “xxxx::/64” and network addresses “xxxx::1”, “yyyy::2”, “aaaa::3”, and “bbbb::4” are assigned respectively to the mobile terminals MN1 to MN4.
In this case, a communication route is established by the highest-layer router R1 so that the network address “xxxx::1” exists in the intermediate layer router Ra, and “yyyy::2”, “aaaa::3”, and “bbbb::4” exists in the intermediate router Rb.
A communication route is established by the intermediate-layer router Ra so that the network address “xxxx::1” exists in the lowest-layer router Rd. A communication route is established by the intermediate-layer router Rb so that the network address “yyyy::2” exists in the lowest-layer router Re. A communication route is established by the lowest-layer router Re so that the network address “aaaa::3” and “bbbb::4” exist in the lowest-layer router Rf.
A communication route is established by the lowest-layer router Rd so that the network address “xxxx::1” exists in the radio base station BS3. A communication route is established by the lowest-layer router Re so that the network address “yyyy::2” exists in the radio base station BS5. A communication route is established by the lowest-layer router Rf so that the communication address “aaaa::3” exists in the radio base station BS7 and the communication address “bbbb::4” exists in the radio base station BS8.
However, a conventional network set-up method has a problem. That is, in the conventional network set-up method, since only the number of routes for a mobile terminal that can be managed by a highest-layer router can be managed by one mobile unit managing network, a wide communication area can not be covered. To solve this problem, a method is required in which when a mobile terminal moves in a wide communication area, two or more mobile unit managing networks are set up in parallel.